This application is based on Japanese Patent Application No. 2000-12515 filed Jan. 21, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates in general to a fluid-filled cylindrical elastic mount which provides a desired vibration damping or isolating effect, utilizing flow of a fluid contained therein, and more particularly to such a cylindrical elastic mount which is easy to manufacture, and which prevents undesirable deformation of components upon assembling these components, thereby exhibiting high stability in quality and improved vibration damping and isolating characteristics of the mount. The present invention is also relates to method of producing the cylindrical elastic mount.
2. Description of the Related Art
A cylindrical elastic mount is known as a vibration damper interposed between two member of a vibration system, to flexibly connecting two members or flexibly mounting one of the two members on the other member. As disclosed in JP-A-10-153233, for example, the cylindrical elastic mount includes a center shaft member and an intermediate metal sleeve member which are disposed in coaxial or eccentric relation with each other, with a suitable radial spacing therebetween, and are connected to each other by an elastic body interposed between the two members. The elastic body has a plurality of pockets formed at respective circumferential portions thereof, which pockets are open in an outer circumferential surface of the intermediate metal sleeve through a plurality of windows formed through the intermediate metal sleeve, respectively. The elastic mount further includes an outer sleeve member which is fitted on the intermediate sleeve so as to close the plurality of windows and which cooperates with the plurality of pockets to define a plurality of fluid chambers filled with a non-compressible fluid, and an orifice member to define orifice passages through which the plurality of chambers communicate with each other. The fluid-filled cylindrical elastic mount as described above utilizes an effect of flow of the fluid, more specifically, the resonance of the fluid flowing through the orifice passage, so as to exhibit a high vibration damping or isolating effect with respect to a vibrational load receiving in directions perpendicular to an axis of the shaft member. This type of elastic mount has been favorably used as an engine mount for a motor vehicle, for example.
The outer sleeve member is fitted on the intermediate metal sleeve by a suitable method. For instance, the outer sleeve member is disposed radially outwardly of the intermediate metal sleeve with a slight radial spacing therebetween. The outer sleeve member is radially inwardly compressed so as to reduce its diameter by effecting a suitable drawing operation which is performed by using eight drawing dies disposed around the outer sleeve member. Thus, the outer sleeve member is fixedly fitted on the outer circumferential surface of the intermediate metal sleeve, thereby closing the openings of the pockets. Alternatively, the outer sleeve member is fitted on the intermediate metal sleeve by a press-fitting operation to press-fit the intermediate metal sleeve in the bore of the outer sleeve member, thereby closing the openings of the pockets. The press-fitting operation permits a rapid and easy assembling of the outer and intermediate sleeve members in comparison with the drawing operation. Further the press-fitting operation may be usable upon assembling an illegally shaped outer sleeve member, such as an outer sleeve including a bracket portion formed as an integral part thereof, with the intermediate metal sleeve.
However, the conventionally employed press-fitting operation, may suffer from inherent problems. Namely, the intermediate metal sleeve member is subjected to resistance force and frictional force applied thereto in its axial direction, upon press-fitting the intermediate metal sleeve member in the bore of the outer sleeve member. This may possibly causes undesirable deformation of the intermediate metal sleeve, especially in circumferential portions where the plurality of windows are formed, since the provision of the windows leads to reduction in a substantial axial dimension and mechanical strength of the intermediate metal sleeve member. The undesirable deformation of the intermediate sleeve not only effects adversely on spring characteristics of the elastic body member, but also possibly causes insufficient fluid-tight sealing between the intermediate and outer sleeve members and a resultant leakage of the fluid from the mount. The conventional elastic mount suffers from a problem of a relatively high ratio of rejects, due to this undesirable deformation of the intermediate metallic sleeve member.
It is therefore an object of the present invention to provide a fluid-filled cylindrical elastic mount which is novel in construction and which is capable of preventing undesirable deformation of an intermediate sleeve member, upon press-fitting the intermediate sleeve member in an outer sleeve member, so that the desired elastic mount can be produced with high stability and ease.
It is another object of the invention to provide a method of producing such a fluid-filled cylindrical elastic mount as described just above.
The first object may be achieved according to the following modes of the invention each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the present invention is not limited to those modes of the invention and combinations of the technical features, but may otherwise be recognized based on the thought of the present invention that disclosed in the whole specification and drawings or that may be recognized by those skilled in the art in the light of the disclosure in the whole specification and drawings.
(1) A fluid filled cylindrical elastic mount including: (a) a center shaft member; (b) an intermediate sleeve member disposed radially outwardly of the center shaft member, the intermediate sleeve member having a plurality of windows formed therethrough, and having a circumferential groove formed in an axially intermediate portion thereof and being open in an outer circumferential surface thereof; (c) an elastic body interposed between the center shaft member and the intermediate sleeve member and having a plurality of pockets formed at respective circumferential positions thereof, the plurality of pockets being open in an outer circumferential surface of the intermediate sleeve member through the plurality of windows, respectively; (d) an outer sleeve member fitted on the intermediate sleeve member so as to close the plurality of windows and cooperating with the plurality of pockets to define a plurality of fluid chambers which are filled with a non-compressible fluid; and (e) an orifice member for defining an orifice passage for fluid communication between the plurality of fluid chambers, the orifice member being disposed in at least one of the plurality of windows so as to extend over an entire circumferential length of the at least one window, and being supported by the intermediate sleeve member such that circumferential opposite end portions of the orifice member are fitted in the circumferential groove on the sides of circumferentially opposite edges of the at least one window, respectively, while having an orifice groove which is formed and open in an outer circumferential surface of said orifice member that is fluid-tightly closed by the outer sleeve member to thereby provide the orifice passage. The orifice member has an axial length which varies in the circumferential direction thereof such that the orifice member is held in abutting contact with axially opposite edges of said at least one of the plurality of windows in a circumferentially intermediate portion of the at least one window, and that the orifice member is spaced apart from at least one of the axially opposite edges of said at least one window in the axial direction thereof in at least one of circumferentially opposite end portions of said at least one window so as to provide opening through which the corresponding pocket is open in the outer circumferential surface of the intermediate sleeve member.
In the fluid-filled cylindrical elastic mount according to the above mode (1) of the present invention, the center shaft member and the intermediate sleeve member are elastically connected to each other by the elastic body which is interposed between and bonded by vulcanization to these two members. The thus obtained intermediate integral vulcanized product is assembled with the orifice member. The intermediate integral vulcanized product with the orifice member mounted is then press-fitted in the bore of the outer sleeve member, so that the outer sleeve member is fitted on the intermediate sleeve member.
According to the above mode (1) of the present invention, the axially opposite edges of the at least one window formed through the intermediate sleeve member are connected with each other in the axial direction of the intermediate sleeve member via the orifice member interposed therebetween. In this arrangement, the mechanical strength of the intermediate sleeve member is sufficiently increased at its circumferential portion where the window is formed, so that the intermediate sleeve member can exhibit sufficient deformation resistance with respect to a load applied thereto in the axial direction thereof. Thus, the intermediate sleeve member of the present elastic mount is less likely to suffer from or is free from a problem of deformation thereof due to the axial load applied thereto when the intermediate sleeve member is press-fitted in the outer sleeve member, so that the present elastic mount can exhibit desired spring characteristics and fluid-tight sealing at the interfaces of the components with high stability. Besides, the intermediate sleeve member of the present elastic mount may facilitate operation for press-fitting the intermediate integral vulcanized product in the bore of the outer sleeve member, resulting in improved efficiency of manufacture of the desired fluid-filled cylindrical elastic mount.
In the intermediate integral vulcanized product on which the orifice member is mounted, the pocket over which the orifice member is disposed is open in the outer circumferential surface of the intermediate sleeve member through the opening formed in at least one of the circumferential opposite end portions of the at least one window. This arrangement facilitates removal of the air from the pocket filled with the non-compressible fluid, resulting in improved efficiency of manufacture of the mount, and improved stability of damping characteristics of the mount.
Preferably, the plurality of fluid chambers includes two fluid chambers which are disposed in the respective circumferential positions that are opposed to each other in a diametric direction of the mount in which a primary vibrational load is applied. The two fluid chambers are communicated with each other through the orifice passage.
(2) A fluid-filled cylindrical elastic mount according to the above-indicated mode (1), wherein the orifice member is held in abutting contact with the axially opposite edges of the at least one of the plurality of windows via a sealing rubber layer interposed therebetween.
In the above mode (2), the orifice member can be easily fitted in the window of the intermediate sleeve member, owing to elastic deformation of the sealing rubber layer interposed between the orifice member and the axially opposite edges of the window, facilitating operation for assembling the orifice member in the intermediate sleeve member. Further, the sealing rubber layer is compressed by and between the axially opposite end faces of the orifice member and the axially opposite edges of the window, whereby the orifice member and the intermediate sleeve member are closely or firmly connected with each other in the circumferential position where the window is formed. Thus, the intermediate sleeve member is reinforced with the orifice member at its circumferential position where the window is formed. Preferably, the sealing rubber layer may be formed on and bonded to the orifice member and/or the intermediate sleeve member. When the sealing rubber layer is formed on the intermediate sleeve member, for example, the sealing rubber layer is integrally formable with the elastic body by simultaneous vulcanization of the elastic body and the sealing rubber layer.
(3) A fluid-filled cylindrical elastic mount according to the above-indicated mode (1) or (2), the at least one of the plurality of windows over which the orifice member extends, has a circumferential length which is not smaller than one-third of the circumference of the intermediate sleeve member.
In the above mode (3), the circumferential length of the window is made larger enough to provide the corresponding fluid chamber with a sufficiently large volume, while the mechanical strength of the intermediate sleeve member is sufficiently reinforced by the orifice member disposed in the window. This arrangement permits a sufficient amount of flow of the fluid flowing through the orifice passage, upon application of a vibrational load to the elastic mount, resulting in improved vibration damping or isolating effect based on the resonance of the flow of the fluid flowing through the orifice passage.
(4) A fluid-filled cylindrical elastic mount according to any one of the above-indicated modes (1)-(3), wherein the plurality of fluid chambers includes a pressure receiving chamber partially defined by the elastic body and being adapted to undergo pressure changes upon application of a vibrational load to the mount, and an equilibrium chamber being diametrically opposite to the pressure receiving chamber and partially defined by a flexible diaphragm, said equilibrium chamber having a volume which is variable due to deformation of the flexible diaphragm. The orifice member is disposed in at least the window through which the pressure-receiving chamber is open in outer circumferential surface of said intermediate sleeve member.
In the above mode (4), the orifice member assembled within the elastic mount such that the orifice member extend along with the inner circumferential surface of the circumferential portion of the outer sleeve member, which circumferential portion partially defines the pressure receiving chamber. The orifice member thus assembled is capable of effectively reinforcing the circumferential portion of the outer sleeve member where the pressure-receiving chamber is partially defined. In this mode, the orifice member is not necessarily required to be disposed on the side of the equilibrium chamber. The absence of the orifice member on the side of the equilibrium chamber permits sufficient amount of volumetric change of the equilibrium chamber, effectively.
(5) A fluid-filled cylindrical elastic mount according to any one of the above-indicated modes (1)-(4), wherein the orifice member is an arquate plate member which extends in a circumferential direction of the intermediate sleeve member and has a pair of axial protrusions formed in a circumferentially intermediate portion thereof so as to protrude outwardly from axially opposite end faces thereof, in axially opposite directions, the pair of axial protrusions having an protruding end faces which are held in abutting contact with circumferentially intermediate portions of said axially opposite edges of the at least one window, respectively, and the orifice member being spaced apart from the axially opposite edges of the at least one window in the axial direction thereof in circumferentially opposite end portions of the at least one window, to thereby provide at each of said circumferentially opposite end portions of the at least one window, two openings which are spaced apart from each other in the axial direction of the orifice member with the orifice member interposed therebetween, through which openings the corresponding pocket being open in the outer circumferential surface of the intermediate sleeve member.
In the fluid-filled elastic mount according to the above mode (5), the axial protrusions of the orifice member is held in abutting contact at their protruding end faces with the axially opposite edges of the at least one window at the circumferentially intermediate portions of the window, resulting in excellent reinforcement of the intermediate sleeve member with the orifice member. The provision of the openings in the circumferentially opposite end portions of the window permits easy introduction of the non-compressible fluid within the pocket through the openings and easy removal of the air undesirably remained within the pocket through the openings, upon filling the pocket with the non-compressible fluid, resulting in improved efficiency of operation for introducing and filling the non-compressible fluid within the pockets.
(6) A fluid-filled cylindrical elastic mount according any one of the above-indicated modes (1)-(5), wherein the orifice member includes a stop portion formed as an integral part thereof, the stop portion extending from an inner surface of the orifice member into the fluid chamber through a central portion of one of said plurality of windows formed through the intermediate sleeve member, so as to opposed to the center shaft member in the diametric direction with a predetermined amount of radial spacing therebetween.
In the above mode (6), the orifice member that has a sufficient strength with respect to the input vibrational load, is effectively utilized to form a stopper mechanism for limiting the amount of relative displacement of the center shaft member and the outer sleeve member in the diametric direction, that is in the load-receiving direction. Further, the orifice member which constitutes the stop portion is directly supported by the outer sleeve member, making it possible that the stop portion exhibits sufficiently large strength resistive to a relatively large load applied thereto.
The second object indicated above may be achieved according to the following mode of the present invention:
(7) A method of producing a fluid-filled cylindrical elastic mount defined in any one of the above-indicated modes (1)-(6), comprising the steps of: assembling the orifice member in an intermediate integral vulcanized product in which the shaft member and the intermediate sleeve member being elastically connected with each other by the elastic body interposed therebetween; and press-fitting the intermediate integral vulcanized product in a bore of said outer sleeve member within a mass of a non-compressible fluid.
According to the method of the above mode (7), the filling of the fluid chambers with the non-compressible fluid can be conducted at the same time when the intermediate integral vulcanized product assembled with the orifice member is press-fitted in the bore of the outer sleeve member. It is appreciated that the outer sleeve member thus fitted on the intermediate integral vulcanized product need not be subjected to a suitable drawing operation, which is performed, for example, by using eight drawing dies disposed around the outer sleeve member. This leads to reduction in number of the manufacturing steps, resulting in improved efficiency of manufacture of the elastic mount.
It is also appreciated that the air remained within the pockets filled with the non-compressible can be easily and steadily removed from the openings formed in at least one of the opposite circumferential end portions of the at least one window of the intermediate sleeve member, and that the presence of the circumferential portion of the orifice member which is interposed between and connected with opposite axial edges of the at least one window, is effective to prevent undesirable deformation of the intermediate sleeve member, in the above-indicated press-fitting operation, permitting manufacture of the desired product with high stability in quality thereof and with ease. Preferably, the intermediate integral vulcanized product is rotated or inclined within the mass of the non-compressible fluid, before executing the press-fitting operation, facilitating elimination or removal of the air remained in the plurality of pockets through the openings.